Thermal defluorination behaviors of PFOS,PFOA and PFBS during regeneration of activated carbon by molten salt

• New method of mineralizing PFCs was proposed. • Activated carbon was regenerated while mineralizing PFCs. • Molten NaOH has good mineralization effect on PFOS and PFBS. Current study proposes a green regeneration method of activated carbon (AC) laden with Perfluorochemicals (PFCs) from the perspective of environmental safety and resource regeneration. The defluorination efficiencies of AC adsorbed perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutanesulfonate (PFBS) using three molten sodium salts and one molten alkali were compared. Results showed that defluorination efficiencies of molten NaOH for the three PFCs were higher than the other three molten sodium salts at lower temperature. At 700°C, the defluorination efficiencies of PFOS and PFBS using molten NaOH reached to 84.2% and 79.2%, respectively, while the defluorination efficiency of PFOA was 35.3%. In addition, the temperature of molten salt, the holding time and the ratio of salt to carbon were directly proportional to the defluorination efficiency. The low defluorination efficiency of PFOA was due to the low thermal stability of PFOA, which made it difficult to be captured by molten salt.The weight loss range of PFOA was 75°C–125°C, which was much lower than PFOS and PFBS (400°C–500°C). From the perspective of gas production, fluorine-containing gases produced from molten NaOH-treated AC were significantly reduced, which means that environmental risks were significantly reduced. After molten NaOH treatment, the regenerated AC had higher adsorption capacity than that of pre-treated AC.     

Worldwide cases of water pollution by emerging contaminants: a review

Environmental Chemistry Letters - Water contamination by emerging contaminants is increasing in the context of rising urbanization, industrialization, and agriculture production. Emerging...     

Treatment and desalination of domestic wastewater for water reuse in a four-chamber microbial desalination cell

Environmental Science and Pollution Research - Microbial desalination cells (MDCs) have been studied for contaminant removal from wastewater and salinity reduction in saline water. However, in an...     

曝气深度对河道底泥特性及水质的影响

采用室内模拟实验方法对受污河道底泥和上覆水进行研究,对比分析静置状态X0和不同曝气深度条件下(分别为水体曝气泥水界面上方10 cm,底泥曝气下方5和15 cm处,依次记为X+10、X-5和X-15)河道底泥特性及水质的影响情况。结果表明:底泥曝气较水体曝气而言,能促进水体DO更快恢复;停止曝气,DO浓度也会维持在较高的状态,有利于有机物和氨氮的进一步去除。在相同曝气量下,底泥曝气比水体曝气能更好地去除底泥中污染物,并减少再次释放,且底泥曝气深度越深,处理效果越好,至实验结束时,X-15组上覆水中COD、NH4+-N、TN及TP浓度分别为16.25、3.03、13.39及0.09 mg/L,去除率分别为69.73%、78.36%、45.98%及84.21%;停止曝气后,经曝气处理的底泥对磷的吸附容量显著增加,并且不会再向上覆水中释放污染物,避免引起水体的二次污染。     

长江中游滨岸带水体氨氮循环速率及影响因素

氨氮(NH_4~+)是大多数浮游生物优先利用的氮源,其在水体中的再生过程(REG)和潜在吸收过程(U_(pot))影响水体初级生产力和生物群落的生长。以长江为研究对象,采用同位素稀释法对长江中游滨岸带水体的NH_4~+循环速率进行研究。结果显示:长江中游滨岸带水体NH_4~+再生速率为0.12～1.62μmol/(L·h),潜在吸收速率为0.21～2.35μmol/(L·h),生物群落NH_4~+需求(CBAD)为0.08～0.75μmol/(L·h)。NH_4~+再生速率、潜在吸收速率和生物群落NH_4~+需求均随水流方向自宜昌至鄱阳湖湖口呈现显著的下降趋势(p0.05)。统计分析表明,化学需氧量(COD)(p0.01)和悬浮物浓度(SS)(p0.05)是影响长江中游水体NH_4~+循环速率的主要因素。长江中游水体NH_4~+再生速率占潜在吸收速率的43.1%～76.0%,均值为58.5±8.5%,表明NH_4~+再生是长江中游水体中生物群落NH_4~+吸收过程的主要NH_4~+来源。估算得到的NH_4~+再生量是长江中游水体TN负荷的2倍,表明水体NH_4~+再生在支持水体初级生产力和维持氮素内循环方面具有重要作用。     

基于目标责任区际优化的耕地保护补偿

耕地保护目标责任与区域补偿标准的合理确定是保证耕地保护区域补偿实施效果的关键。针对以往耕地保护目标责任忽视耕地资源禀赋与社会经济发展差异的不足,本文构建分区异步元胞自动机模型开展了耕地区际布局优化,并据此优化区域耕地保护目标责任。在此基础上,针对当前研究中耕地保护区域补偿标准与耕地非农化收益及耕地赤字/盈余水平脱节、难以真正起到耕地保护杠杆作用的不足,本文提出了以耕地资源价值为基础,引入耕地非农化收益确定耕地保护区域补偿标准,并根据耕地保护目标责任优化结果测算区域耕地赤字/盈余水平对耕地保护区域补偿价值标准进行修正,以实现"以布局引导补偿,以补偿实现保护"。以全国首批"两型社会"建设试验区武汉城市圈为案例区开展了实证研究,结果表明:1根据资源禀赋与经济发展区域差异确定区域耕地保护目标责任可以在实现全区域粮食安全的基础上使区域耕地非农化压力得到最大限度的释放,有利于耕地保护目标的实现;2以耕地非农化收益和耕地资源价值为基础,采用区域耕地赤字/盈余进行修正得到耕地保护区域补偿标准,可以起到激励耕地保护的杠杆作用;3基于目标责任区际优化的耕地保护区域补偿是协调我国快速城镇化进程中城镇用地扩张与耕地保护矛盾的重要途径,能起到激励耕地保护、抑制耕地非农化的作用。     

水体环境中氟喹诺酮类药物的污染现状及分析方法

阐述了水体环境中的氟喹诺酮类（FQs）药物的来源和污染现状,介绍了FQs在水体环境中的迁移、转化和转归途径,归纳了各种当前使用较多的FQs分析检测方法的功能特点和适用条件。指出今后在FQs分析技术的开发上,应注重提高检测容量、降低检出限和削减环境负面影响因素。     

炼油催化剂废渣污染及其防治的研究

对炼油厂裂化催化剂废渣和加氢精制催化剂渣的污染成分和污染状况进行了分析,结果表明,排放到大气中的裂化催化剂微粒含有０．５５％的Ｎｉ和０．１８％的Ｖ,已造成大气污染,裂化催化剂废渣经雨水淋洗后,其中部分Ｎｉ和Ｖ会进入水环境,造成污染。     

玉环电厂1 000 MW机组降低Nox排放的技术分析与环境评价

介绍了玉环电厂采用PM型燃烧器和MACT分级燃烧技术,降低了NOx生成量.预测不同负荷下的NOx排放浓度,对照《火电厂大气污染物排放标准》,分析玉环电厂的环境性能,为其他电厂降低NOx排放提供借鉴.